The present invention relates to a heat exchanger such as a heat exchanger having fins or a double tube heat exchanger mainly used in an air conditioner.
As shown in FIG. 8, a conventional heat exchanger having fins comprises fins 201 arranged at a predetermined distance from one another, and heat exchanger tubes 202 inserted through fin surfaces of the fins 201 perpendicularly to the latter. A current 203 of air flows in the direction of the arrow between the fins, and exchanges heat with fluid flowing the passages of the heat exchanger tubes 202. When such a heat exchanger having fins is used, it is common that an end portion thereof is bent at a predetermined radius of curvature R, and the heat exchanger is accommodated in an outdoor unit of an air conditioner.
First prior art (Japanese Patent Application Laid-open No.S61-15089) is shown in FIGS. 9a and 9b. 
FIG. 9a is a vertical sectional view showing a portion of a heat exchanger tube, and FIG. 9b is an enlarged sectional view of an essential portion showing an inner wall surface of the heat exchanger tube.
According to the first prior art of the heat exchanger, a coil 204 comprising spirally wound metal fine wire is inserted into a heat exchanger tube 202, an outer periphery of this coil 204 is tightly fixed to an inner surface of the heat exchanger tube 202, and a large number of powdery members 205 are jointed to the inner surface of the heat exchanger tube 202 to form a porous material layer.
According to this structure, heat transfer area of the inner surface of the heat exchanger tube 202 is increased, a turbulent flow effect, a capillary action effect and a nucleate boiling effect are exhibited to enhance the heat transfer performance.
Second prior art (Japanese Utility Model Registration Application Laid-open No.S58-52491) is shown in FIG. 10.
FIG. 10 is a sectional view of a heat exchanger having fins taken along the surface passing through the center of a heat exchanger tube thereof.
According to the second prior art, a spacer 206 which can be deformed by heat is inserted into a heat exchanger tube 202, and after the insertion, the spacer 206 is heated so that the spacer 206 is tightly adhered to an inner wall of the tube. A fin group 201 is jointed to an outer peripheral surface of the heat exchanger tube 202.
With this structure, the heat transfer area of the inner surface of the heat exchanger tube 202 is increased, and a turbulent flow effect is exhibited to enhance the heat transfer performance.
Third prior art (Japanese Patent Application No.H10-2638) is shown in FIG. 11.
FIG. 11 is a perspective view showing a structure of a heat exchanger having fins.
According to the third prior art, in the heat exchanger having fins functioning as a condenser, the number of paths of an outlet tube 207 for refrigerant is reduced, the outlet tube 207 is disposed in the windward side with respect to the direction 203 of air flow, and a fin 201 between the adjacent tubes 202 at the downwind side is provided with a slit 208 in the longitudinal direction of the fin 201.
With this structure, it is regarded that when the heat exchanger is used as a condenser, since it is possible to increase the speed in the tube mainly by the outlet tube 207 which is excessively cooled region, the heat transfer performance is enhanced, and by disposing the excessively cooled region having low temperature in the windward side, it is possible to increase the temperature difference between the air and the excessively cooled region, and the condense performance can be enhanced.
Forth prior art (Japanese Patent Application No.S57-127732) is shown in FIG. 12.
FIG. 12 is a perspective view showing a structure of a heat exchanger having fins.
According to the fourth prior art, in the heat exchanger having fins functioning as a condenser, the diameter of an outlet tube 209 of refrigerant is made thinner than those of other portions.
According to this structure, it is regarded that when the heat exchanger is used as a condenser, since it is possible to increase the speed in the tube by the outlet tube 209 which is excessively cooled region, the heat transfer performance is enhanced, and by disposing the excessively cooled region having low temperature in the windward side, it is possible to increase the temperature difference between the air and the excessively cooled region, and the condense performance can be enhanced.
Fifth prior art (Japanese Patent Application No.H2-103355) is shown in FIGS. 13a and 13b. 
FIG. 13a is a perspective view showing a structure of a heat exchanger having fins, and FIG. 13b is a sectional view of a heat exchanger tube constituting the heat exchanger.
According to the fifth prior art, in the heat exchanger having fins functioning as a condenser, inner rods 211 are inserted in the heat exchanger tube 210 in the vicinity of the refrigerant outlet.
With this structure, it is regarded that the heat exchanger having fins used as the condenser can reduce the amount of refrigerant charged by the inner rods 211 inserted in the excessive cooled regions.
However, according to the structure of the first prior art, since a wire of very small diameter is used as the coil, the volume of the tube can not be remarkably reduced by inserting the coil. Further, when the heat exchanger is used as a condenser, the inner surface of the tube which is the heat transfer surface is liable to be covered with a thick condensed liquid film and there is a problem that the heat exchanging performance is lowered.
According to the structure of the second prior art, since this prior art mainly aims at increasing the heat transfer area of the inner surface of the heat transfer tube and at the turbulent flow effect, and the thickness of the spacer is not specified, it is judged that the thickness of the spacer is equal to that of the heat exchanger tube, and the volume of the tube can not be remarkably reduced by inserting the coil. Further, when the heat exchanger is used as a condenser, the inner surface of the tube which is the heat transfer surface is liable to be covered with a thick condensed liquid film and there is a problem that the heat exchanging performance is lowered.
According to the structure of the third prior art, the current speed can be increased by minimizing the number of paths, but the current speed of the minimum paths is the highest, and it is not possible to further enhance the speed. Further, the speed can only be changed at least for one heat exchanger tube by on heat exchanger tube. It is not possible to reduce the volume in the tube. Further, when the heat exchanger is used as a condenser, the inner surface of the tube which is the heat transfer surface is liable to be covered with a thick condensed liquid film and there is a problem that the heat exchanging performance is lowered.
According to the structure of the fourth prior art, the current speed in the thin tube can be increased, and the current speed can be arbitrarily determined by selecting the diameter of the thin tube, but in order to change the diameter of the thin tube, it is necessary to change the molding dies of the fin having a hole in which the thin tube is inserted. Therefore, it is necessary to make a significant investment in the molding dies, and it is not easy to change the diameter. It is not possible to reduce the volume in the tube. Further, when the heat exchanger is used as a condenser, the inner surface of the tube which is the heat transfer surface is liable to be covered with a thick condensed liquid film and there is a problem that the heat exchanging performance is lowered.
According to the structure of the fifth prior art, this is only effective to reduce the amount of refrigerant when the heat exchanger is used as a condenser. When the heat exchanger is used as an evaporator, since it is described that a member which satisfies the pressure of 4 kg/cm2 is inserted to the outlet of the condenser, this will bring about a remarkable increase in pressure loss, and there is a problem that the evaporation ability is remarkably lowered.
The present invention has been accomplished to solve the problems of the prior art, and it is an object of the invention to enhance the evaporation ability or to restrain the evaporation ability from lowering while restraining the pressure loss at the time of evaporation by inserting, into a heat exchanger tube, a member which reduces the refrigerant flow passage as the mass flow rate quality (dryness fraction) is increased.
Further, when the heat exchanger is used as a condenser, it is another object of the invention to provide a heat exchanger capable of reducing the thickness of the liquid film of an inner surface of a tube by adhering the condensed liquid to an outer surface of a member inserted into two-phase region, reducing the cross-sectional area of the flow passage in the heat exchanger tube by the insertion member, enhancing the current flow of the refrigerant flowing in the heat exchanger tube, and enhancing the heat exchanging performance.
Furthermore, it is another object of the invention to provide a heat exchanger capable of reducing the amount of refrigerant to be charged by reducing the volume in the heat exchanger tube.
According to a first aspect, there is provided a heat exchanger for exchanging heat between fluid flowing in a flow passage in a heat exchanger tube and fluid flowing outside of the heat exchanger tube, wherein a solid bar-like insertion member or a hollow bar-like insertion member whose opposite ends are closed is provided in the flow passage in which a fluid having phase change flows in gas-liquid two phase state or liquid phase state, a cross section of the insertion member is formed into a substantially circle shape, a polygonal shape or a starlike shape, and a cross-sectional area of a flow passage in which the fluid flows is reduced as a mass flow rate quality of the fluid is reduced.
According to this construction, since the influence of the pressure loss is increased as the mass flow rate quality is increased, the pressure loss can effectively be reduced by widening the flow passage having great mass flow rate quality, and the evaporation ability can be enhanced or restrained from lowering. When the heat exchanger is used as a condenser, if the current speed of the refrigerant flowing in the heat exchanger tube in a flow passage having small mass flow rate quality is increased, it is possible to reduce the thickness of the liquid film of the inner surface of the tube due to the condensed liquid, and it is possible to obtain a heat exchanger having high heat exchanging performance in the tube. Further, since the area of the outer surface of the insertion member is increased by forming the cross section of the insertion member into polygonal shape or starlike shape, the amount of condensed liquid adhered to the insertion member is increased, and it is possible to further reduce the thickness of the condensed liquid film on the inner peripheral surface of the heat exchanger tube, and to enhance the heat transfer coefficient. Further, since the volume in the heat exchanger tube can be reduced, the amount of refrigerant to be charged can be reduced.
According to a second aspect, there is provided a heat exchanger for exchanging heat between fluid flowing in a flow passage in a heat exchanger tube and fluid flowing outside of the heat exchanger tube, wherein a bar-like insertion member is provided in the flow passage in which a fluid having phase change flows in gas-liquid two phase state or liquid phase state, and a cross-sectional area of a flow passage in which the fluid flows is reduced as a mass flow rate quality of the fluid is reduced.
According to this construction, since the influence of the pressure loss is increased as the mass flow rate quality is increased, the pressure loss can effectively be reduced by widening the flow passage having great mass flow rate quality, and the evaporation ability can be enhanced or restrained from lowering. When the heat exchanger is used as a condenser, if the current speed of the refrigerant flowing in the heat exchanger tube in a flow passage having small mass flow rate quality is increased, it is possible to reduce the thickness of the liquid film of the inner surface of the tube due to the condensed liquid, and it is possible to obtain a heat exchanger having high heat exchanging performance in the tube. Further, since the volume in the heat exchanger tube can be reduced, the amount of refrigerant to be charged can be reduced.
According to a third aspect, in the first or second aspect, a cross-sectional area of the insertion member is discontinuously varied.
According to this construction, it is possible to reduce the cross-sectional area of the flow passage in which the fluid flows can be reduced as the mass flow rate quality of the fluid is reduced by varying the cross-sectional area of the insertion member. Further, it is possible to easily change the cross-sectional area of the flow passage by combining insertion members having different diameters.
According to a fourth aspect, in the first or second aspect, a cross-sectional area of the insertion member is continuously varied.
According to this construction, it is possible to reduce the cross-sectional area of the flow passage in which the fluid flows can be reduced as the mass flow rate quality of the fluid is reduced by varying the cross-sectional area of the insertion member. Further, it is possible to optimally reduce the pressure loss and to exploit the full heat exchanging performance by continuously changing the cross-sectional area of the insertion member.
According to a fifth aspect, there is provided a heat exchanger for exchanging heat between fluid flowing in a flow passage in a heat exchanger tube and fluid flowing outside of the heat exchanger tube, wherein a solid bar-like insertion member or a hollow bar-like insertion member whose opposite ends are closed is provided in the flow passage in which a fluid having phase change flows in gas-liquid two phase state or liquid phase state, and a cross section of the insertion member is formed into a substantially circle shape, a polygonal shape or a starlike shape.
According to this construction, when the heat exchanger is used as a condenser, the thickness of the liquid film of the inner surface of the tube by the condensed liquid in the two-phase region or liquid phase can be reduced, and the current speed of the refrigerant flowing in the heat exchanger tube can be enhanced so that a heat exchanger having high heat exchanging performance in the tube can be obtained. Further, since the area of the outer surface of the insertion member is increased by forming the cross section of the insertion member into polygonal shape or starlike shape, the amount of condensed liquid adhered to the insertion member is increased, and it is possible to further reduce the thickness of the condensed liquid film on the inner peripheral surface of the heat exchanger tube, and to enhance the heat transfer coefficient. Further, since the volume in the heat exchanger tube can be reduced, the amount of refrigerant to be charged can be reduced.
According to a sixth aspect, in any one of the first, second and fifth aspects, the insertion member is provided on its outer surface with a groove, or a bump and a dip.
According to this construction, since the area of the outer surface of the insertion member is increased, the amount of condensed liquid adhered to the insertion member is increased, and it is possible to further reduce the thickness of the condensed liquid film on the inner peripheral surface of the heat exchanger tube, and to enhance the heat transfer coefficient.
According to a seventh aspect, in any one of the first, second and fifth aspects, the insertion member is made of porous material.
According to this construction, since the area of the outer surface of the insertion member is increased by the porous material, the amount of condensed liquid adhered to the insertion member is increased, and it is possible to further reduce the thickness of the condensed liquid film on the inner peripheral surface of the heat exchanger tube, and to enhance the heat transfer coefficient.
According to an eighth aspect, in any one of the first, second and fifth aspects, the insertion member is provided in plural into bundle.
According to this construction, since the plurality of insertion members are provided, the area of the outer surfaces of the insertion members is increased, the amount of condensed liquid adhered to the insertion member is increased, and it is possible to further reduce the thickness of the condensed liquid film on the inner peripheral surface of the heat exchanger tube, and to enhance the heat transfer coefficient.
According to a ninth aspect, in any one of the first, second and fifth aspects, a refrigerant comprising hydro fluorocarbon (HFC) or hydrocarbon (HC) as main component is used as the fluid flowing in the flow passage in the heat exchanger tube.
According to this construction, the refrigerant comprising hydro fluorocarbon (HFC) or hydrocarbon (HC) as main component has higher refrigerant density at the same cycle point than conventional R22 and thus has lower current speed, and the pressure loss is lowered to about 70% when the refrigerant has the same ability as the conventional R22. For this reason, the heat transfer coefficient is enhanced and the heat exchanging coefficient is also enhanced especially by using R410A, propane (R290) or the like as refrigerant. Further, if the hydro fluorocarbon (HFC) or hydrocarbon (HC) is used, the value of the ozone destroy potential (ODP) is 0. Although the value of the global warming potential (GWP) of the hydro fluorocarbon (HFC) is high, the global warming potential (GWP) of the hydrocarbon (HC) is extremely closer to 0. Therefore, the environmental problem can be overcome.
According to a tenth aspect, in the third aspect, the insertion member is provided on its outer surface with a groove, or a bump and a dip.
According to this construction, since the area of the outer surface of the insertion member is increased, the amount of condensed liquid adhered to the insertion member is increased, and it is possible to further reduce the thickness of the condensed liquid film on the inner peripheral surface of the heat exchanger tube, and to enhance the heat transfer coefficient.
According to an eleventh aspect, in the third aspect, the insertion member is made of porous material.
According to this construction, since the area of the outer surface of the insertion member is increased by the porous material, the amount of condensed liquid adhered to the insertion member is increased, and it is possible to further reduce the thickness of the condensed liquid film on the inner peripheral surface of the heat exchanger tube, and to enhance the heat transfer coefficient.
According to a twelfth aspect, in the third aspect, the insertion member is provided in plural into bundle.
According to this construction, since the plurality of insertion members are provided, the area of the outer surfaces of the insertion members is increased, the amount of condensed liquid adhered to the insertion member is increased, and it is possible to further reduce the thickness of the condensed liquid film on the inner peripheral surface of the heat exchanger tube, and to enhance the heat transfer coefficient.
According to a thirteenth aspect, in the third aspect, a refrigerant comprising hydro fluorocarbon (HFC) or hydrocarbon (HC) as main component is used as the fluid flowing in the flow passage in the heat exchanger tube.
According to this construction, the refrigerant comprising hydro fluorocarbon (HFC) or hydrocarbon (HC) as main component has higher refrigerant density at the same cycle point than conventional R22 and thus has lower current speed, and the pressure loss is lowered to about 70% when the refrigerant has the same ability as the conventional R22. For this reason, the heat transfer coefficient is enhanced and the heat exchanging coefficient is also enhanced especially by using R410A, propane (R290) or the like as refrigerant. Further, if the hydro fluorocarbon (HFC) or hydrocarbon (HC) is used, the value of the ozone destroy potential (ODP) is 0. Although the value of the global warming potential (GWP) of the hydro fluorocarbon (HFC) is high, the global warming potential (GWP) of the hydrocarbon (HC) is extremely closer to 0. Therefore, the environmental problem can be overcome.
According to a fourteenth aspect, in the fourth aspect, the insertion member is provided on its outer surface with a groove, or a bump and a dip.
According to this construction, since the area of the outer surface of the insertion member is increased, the amount of condensed liquid adhered to the insertion member is increased, and it is possible to further reduce the thickness of the condensed liquid film on the inner peripheral surface of the heat exchanger tube, and to enhance the heat transfer coefficient.
According to a fifteenth aspect, in the fourth aspect, the insertion member is made of porous material.
According to this construction, since the area of the outer surface of the insertion member is increased by the porous material, the amount of condensed liquid adhered to the insertion member is increased, and it is possible to further reduce the thickness of the condensed liquid film on the inner peripheral surface of the heat exchanger tube, and to enhance the heat transfer coefficient.
According to a sixteenth aspect, in the fourth aspect, the insertion member is provided in plural into bundle.
According to this construction, since the plurality of insertion members are provided, the area of the outer surfaces of the insertion members is increased, the amount of condensed liquid adhered to the insertion member is increased, and it is possible to further reduce the thickness of the condensed liquid film on the inner peripheral surface of the heat exchanger tube, and to enhance the heat transfer coefficient.
According to a seventeenth aspect, in the fourth aspect, a refrigerant comprising hydro fluorocarbon (HFC) or hydrocarbon (HC) as main component is used as the fluid flowing in the flow passage in the heat exchanger tube.
According to this construction, the refrigerant comprising hydro fluorocarbon (HFC) or hydrocarbon (HC) as main component has higher refrigerant density at the same cycle point than conventional R22 and thus has lower current speed, and the pressure loss is lowered to about 70% when the refrigerant has the same ability as the conventional R22. For this reason, the heat transfer coefficient is enhanced and the heat exchanging coefficient is also enhanced especially by using R410A, propane (R290) or the like as refrigerant. Further, if the hydro fluorocarbon (HFC) or hydrocarbon (HC) is used, the value of the ozone destroy potential (ODP) is 0. Although the value of the global warming potential (GWP) of the hydro fluorocarbon (HFC) is high, the global warming potential (GWP) of the hydrocarbon (HC) is extremely closer to 0. Therefore, the environmental problem can be overcome.